Paper currency validator

ABSTRACT

The frequency-sensing circuit of a paper currency validator uses fixed, rather than adjustable, components to sense a predetermined frequency; and an adjustable speed D.C. motor is set to drive the vertical grid lines in the portrait background of a bill past the air gap of a magnetic head at a selected rate to develop signals of that predetermined frequency. That frequency-sensing circuit is much more stable and much less expensive than a frequency-sensing circuit which uses adjustable components, and that D.C. motor is much smaller and much less expensive than a synchronous motor of comparable power. That D.C. motor causes bill-driving members to move a bill past a billactuated switch and then past that magnetic head; and a timing circuit will reverse that motor, to cause those bill-driving members to move that bill back outwardly of that paper currency validator, if that magnetic head does not coact with the frequency-sensing circuit to develop a validation signal within a predetermined length of time. A sub-circuit senses the current flowing to the motor; and, if a person attempts to retard or halt the inward movement of a bill, the value of the motor current will increase, and the current-sensing sub-circuit will respond to the increase in motor current to inhibit the development of a validation signal. The paper currency validator has a billactuated start switch, a bill-actuated sequence switch and a bill-actuated exit switch; and those switches are normally connected to the rest of the circuitry of that paper currency validator. However, as soon as a validation signal is developed, all of those switches are immediately isolated from the rest of that circuitry; and this is desirable, because it keeps any further closing of any of those switches from affecting the rest of that circuitry. In this way, any undesirable effect from &#39;&#39;&#39;&#39;contact bounce&#39;&#39;&#39;&#39; or from the deliberate closing of any of those switches is completely obviated. If a person attempts, in an unauthorized manner, to cause the paper currency validator to supply a vend signal, the motor of that paper currency validator will automatically reverse and thereby cause the bill-driving members to return to that person any bill or other object which was being used in that attempt. In addition, that paper currency validator will cancel any validation signal which had been developed as a result of the insertion of that bill or other object. The paper currency validator disposes one magnetic head so it can sense the vertical grid lines in one quadrant of the portrait background of a bill and disposes a second magnetic head so it can sense the vertical grid lines in the diagonallydisplaced quadrant of that portrait background; and it requires those magnetic heads to simultaneously supply signals of essentially the same frequency. The paper currency validator disposes bill-driving members immediately outwardly of the first magnetic head, and it also provides a sub-circuit which will reverse the motor if the leading edge of a bill is not able to move a fixed distance beyond that magnetic head within a predetermined length of time. Because those bill-driving elements are disposed immediately outwardly of that magnetic head, they will remain in engagement with the trailing edge of that bill even if substantially the entire length of that bill is wrinkled and crumbled up against that magnetic head; and that sub-circuit will reverse the motor, and thereby enable the bill-driving members to move thaT bill back outwardly of the paper currency validator, before those bill-driving members could tear or otherwise degrade that bill.

United States Patent [191 c Fishel et al;

[ Oct. 29, 1974 PAPER CURRENCY VALIDATOR [73] Assignee: UMC Industries, Inc., New York,

22] Filed: oct.13,1972

21 Appl. No.: 297,321

Primary Examinerl larold l. Pitts 5 7] ABSTRACT The frequency-sensing circuit of a paper currency validator uses fixed, rather than adjustable, components to sense a predetermined frequency; and an adjustable speed DC. motor is set to drive the vertical grid lines in the portrait background of a bill past the air gap of a magnetic head at a selected rate to develop signals of that predetermined frequency. That frequency-sensing circuit is much more stable and much less expensive than a frequency-sensing circuit which uses adjustable components, and that DC. motor is much smaller and much less expensive than a synchronous motor of comparable power. That DC. motor causes bill-driving members to move a bill past a bill-actuated switch and then past that magnetic head; and a timing circuit will reverse that motor, to cause those bill-driving members to move that bill back outwardly of that paper currency validator, if that magnetic head does not coact with the frequencysensing circuit to develop a validation signal within a predetermined length of time. A sub-circuit senses the current flowing to the motor; and, if a person attempts to retard or halt the inward movement of a bill, the value of the motor current will increase, and the current-sensing sub-circuit will respond to the increase in motor current to inhibit the development of a validation signal. The paper currency validator has a billactuated start switch, a bill-actuated sequence switch and a bill-actuated exit'switch; and those switches are normally connected to the rest of the circuitry of that paper currency validator. However, as soon as a validation signal is developed, all of those switches are immediately isolated from the rest of that circuitry; and

this is desirable, because it keeps any further closing of any of those switches from affecting the rest of that circuitry. In this way, any undesirable effect from contact bounce or from the deliberate closing of any of those switches is completely obviated. If a person attempts, in an unauthorized manner, to cause the paper currency validator to supply a vend signal, the motor of that paper currency validator will automatically reverse and thereby cause the bill-driving members to return to that person any bill or other object which was being used in that attempt. in addition, that paper currency validator will cancel any validation signal which had been developed as a result of the insertion of that bill or other object. The paper currency validator disposes one magnetic head so it can sense the vertical grid lines in onequadrant of the portrait background of a bill and disposes a second magnetic head so it can sense the vertical grid lines in the diagonally-displaced quadrant of that portrait background; and it requires those magnetic heads to simultaneously supply signals of essentially the same frequency. The paper currency validator disposes billdriying members immediately outwardly of the first magnetic head and it also provides a sub-circuit which will reverse the motor if the leading edge of a bill isnot able to move a fixed distance beyond that magnetic head within a predetermined length of time. Because those bill-driving elements are disposed immediately outwardly of that magnetic head, they will remain in engagement with the trailing edge of that bill even if substantially the entire length of that bill is wrinkled and crumbled, up against that magnetic head; and that sub-circuit will reverse the motor, and

, thereby enable the bill-driving members to move that bill back outwardly of the paper currency validator, before those bill-driving members could tear or otherwise degrade that bill.

22 Claims, 15 Drawing Figures PATENTED GET 2 9 1974 saw: a w s PAPER CURRENCY VALIDATOR SUMMARY OF THE INVENTION This invention relates to improvements in paper cur- 5 rency validators. More particularly, this invention relates to improvements in paper currency validators wherein the movement of an authentic bill past a sensing device will develop signals having a predetermined frequency.

it is, therefore, an object of the present invention to provide an improved paper currency validator which develops a predetermined frequency as an authentic bill is moved past a sensing element.

Prior paper currency validators, which moved bills l5 through them at predetermined rates to develop signals of predetermined frequencies, used synchronous motors to drive those bills; and they used adjustable components in the frequency-sensing circuits thereof to make the center frequencies of those frequencysensing circuits match those predetermined frequencies. However, adjustable inductors are less stable and more expensive than fixed inductors of comparable quality, and adjustable capacitors are less stable and more expensive than fixed capacitors of comparable quality; and hence paper currency validators which use frequency-sensing circuits that utilize adjustable components are less stable and more expensive than would be a paper currency validator which uses a frequency sensing circuit that utilizes fixed components.

The paper currency validator of the present invention is able to use a frequency-sensing circuit which utilizes fixed components because it utilizes an adjustable speed D.C. motor that has the speed thereof closely regulated. That adjustable speed D.C. motor is adjusted to drive the vertical grid lines in the portrait background of a bill past the air gap of a magnetic head at a rate which will enable that magnetic head to develop signals which have a frequency that matches the frequency of the frequency-sensing circuit of that paper currency validator. The present invention thus makes the speed of the adjustable speed D.C. motor thereof a function of the frequency of the frequency-sensing circuit thereof rather than vice versa; and, in doing so, that paper currency validator makes it possible to use a much more stable but much less expensive frequencysensing circuit, and also makes it possible to use a much smaller and much less expensive motor. It is, therefore, an object of the presentinvention to provide a paper currency validator with an adjustable speed D.C. motor which can move bills through that paper currency validator at a rate which is a function of the center frequency of a frequency-sensing circuit that uses fixed components.

The D.C. motor of the paper currency validator of the present invention causesbill-driving members to move a bill past a bill-actuated switch and then past a magnetic head; and a timingcircuit will reverse that motor, to cause those bill-driving members to move that bill back outwardly of that paper currency validator. if that'magnetic head does not coact with the frequency-sensing circuit to develop a validation signal within a predetermined-length of time. In doing so, that timing circuit keeps the bill from moving so far inwardly of the paper currency validator that the billdriving members would be unable to move that bill back outwardly of that paper currency validator. Also,

in doing so, that timing circuit limits the length of time during which that bill is adjacent that magnetic head, and thereby correspondingly reduces the likelihood that a person could manipulate that bill and cause it to coact with that magnetic head to develop signals of the required frequency. It is, therefore, an object of the present invention to provide a paper currency validator wherein a motor causes bill-drivingmembersto move a bill past a bill-actuated switch and then past a magnetic head, and wherein a timing circuit will reverse that motor, to cause those bill-driving members to move that bill back outwardly of that paper currency validator, if that magnetic head does not coact with the frequency-sensing circuit to develop a validation signal within a predetermined length of time.

The motor of the paper currency validator of the present invention causes the bill-driving members thereof to move at a fixed rate of speed; and, once that motor has gotten those bill-driving members up to that rate of speed, it will draw an approximately constant value of current. That motor and those bill-driving members will resist any efforts of a person to retard or stop the movement of a bill inwardly of the paper currency validator; and, in doing so, that motor will draw increased values of current. A sub-circuit senses the value of the current drawn by the motor; and, if a person attempts to retard or halt the inward movement of a bill, that sub-circuit will respond to the consequent increase-in the value of the motor current to inhibit the development of a validation signal. Thismeans that if a person was able to retard or stop the inward movement of a bill, that person would not be able to effect the unauthorized vending of a product from the 'vending machine, to which the paper currency validator is connected, because the current-sensing sub-circuit would prevent the development of a validation signal. It is, therefore, an object of the present invention to provide a paper currency validator with a currentsensing sub-circuit which will respond to undue increases in the value of the motor current to inhibit the development of a validation signal.

The paper currency validator of the present invention has a bill-actuated start switch, a bill-actuated sequence switch and a bill-actuated exit switch; and those bill-actuated switches are normally connected to the rest of the circuitry of that paper currency validator. However, as soon as a validation signal is developed, all of those bill-actuated switches are immediately isolated from the rest of that circuitry; and this is desirable, because it will keep any further closing or opening of any of those switches from affectingthat circuitry. In this way, any undesirable effects on the operation of the rest of that circuitry, which are due to contact bounce or to the deliberate closing and opening of any of those switches,- will be obviated. It is, therefore, an object of the present invention to provide a paper currency validator which has bill-actuated switches that are initially connected tothe rest of the circuitry of that paper currency validator but which are immediately isolated from the rest of that circuitry as soon as a validation signal is developed.

If a person inserts a short length of a bill into the paper currency validator of the present invention, attaches a tape, thread or other tail to, a bill, disconnects and then reconnects the line cord of the paper currency validator, or otherwise attempts to obtain an improper operation of that paper currency validator,

the motor of that paper currency validator will reverse and thereby cause the bill-driving members to move any inserted bill or the like back outwardly of that paper currency validator. In addition, that paper currency validator will automatically cancel any validation signal which was previously developed as the cropped bill or tail-equipped bill was moved inwardly of that paper currency validator. In this way, the present invention returns all cropped bills and tail-equipped bills so other persons can subsequently insert proper bills; and it also automatically cancels any validation signal which that cropped bill or tail-equipped bill might have developed. It is, therefore, an object of the present invention to provide a paper currency validator which can return all cropped bills or tail-equipped bills by reversing the motor thereof, and which will automatically cancel any validation signal which that cropped bill or tail-equipped bill might have developed.

The paper currency validator of the present invention disposes one magnetic head so it senses the vertical grid lines in one quadrant of the portrait background of a bill and disposes a second magnetic head so it senses the vertical grid lines in the diagonally-displaced quadrant of that portrait background. In addition, that paper currency validator will provide a validation signal only if both of those magnetic heads simultaneously sense vertical grid lines of predetermined spacing within those diagonally displaced quadrants'of the portrait background. By disposing the two magnetic heads so they must sense vertical grid lines in diagonallydisplaced quadrants of the portrait background of a bill, the paper currency validator of the present invention avoids the development ofa validation signal in the event a person inserts just the upper half, just the lower half, just the Ieft-hand half, or just the right-hand half of a bill. By requiring the two magnetic heads to simultaneously sense vertical grid lines of predetermined spacing within the diagonally-displaced quadrants of the portrait background of each bill. the paper currency validator avoids the cost and space of the subcircuit which would be needed to hold a first frequency-initiated signal until a second frequency-initiated signal was developed. It is, therefore, an object of the present invention to provide a paper currency validator which disposes one magnetic head so it will sense vertical grid lines in one quadrant of the portrait background of a bill, to mount a second magnetic head so it will sense vertical grid lines in the diagonallydisplaced quadrant of that portrait background, and to develop a validation signal only if those magnetic heads simultaneously sense vertical grid lines of predetermined spacing within those diagonally-displaced quadrants.

The paper currency validator of the present invention disposes some bill-driving members thereof immediately outwardly of a magnetic head thereof, and provides a sub-circuit which will reverse the motor thereof if the leading edge of any bill does not move a fixed distance inwardly of that magnetic head within a predetermined length of time. The bill-driving members are spaced so close to that magnetic head that even if no portion of that bill is able to pass by that magnetic head and hence substantially all portions of the length of that bill become wrinkled and crumpled up adjacent that magnetic head. those bill-driving members will still be in engagment with the trailing edge of thatbill. The

sub-circuit will promptly reverse the motor and cause the bill-driving members to move the bill back outwardly of the paper currency validator thereby clearing the paper currency validator so further bills can be accepted by it. That sub-circuit will reverse the motor and causethe bill-driving members to move the bill back outwardly of the paper currency validator before those bill-driving members would have time to tear or otherwise degrade the bill. It is, therefore, an object of the present invention to provide a paper currency validator which disposes some bill-driving members thereof immediately outwardly of a magnetic head thereof and which provides a sub-circuit that will reverse the motor thereof if the leading edge of a bill does not move a predetermined distance inwardly of that magnetic head within a predetermined length of time.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description a preferred embodiment of the present invention is shown and described but it is to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, FIG. 1 is a perspective view of one preferred embodiment of paper currency validator that is made in accordance with the principles and teachings of the present invention, v

FIG. 2 is a partially-broken elevational viewof the front of the paper currency validator of FIG. 1,

FIG. 3 is an elevational view of the rear of the paper currency validator of FIG. 1,

FIG. 4 is a sectional view through the paper currency validator of FIG. 1, and it is taken along the plane indicated by the line 4-4 in FIG. 2, v

FIG. 5 is another sectional view through the paper currency validator of FIG. 1, and it is taken along the plane indicated by the line 55 in FIG. 2,

FIG. 6 is a bottom view of the cover and associated parts of the paper currency validator of FIG. 1, and it is taken along the plane indicated by the line 6-6 in FIG. 3,

FIG. 7 is a partially broken-away, plan view of the paper currency validator of FIG. 1 with the cover and associated parts removed, and it is taken along the plane indicated by the line 7-7 in FIG. 5,

FIG. 8 is a bottom view of a portion of the paper currency validator of FIG. 1, and it taken along the plane indicated by the line 8--8 in FIG. 5,

FIG. 9 is a sectional view through one of the pressure rollers, and is an end elevational view of one of the magnetic heads, of the paper currency validator of FIG. I, and it is taken along the plane indicated by the line 99 in FIG. 10,

FIG. 10 is a side elevational view of the magnetic head and of the pressure roller shown in F IG. 9,

The diagram at the right of FIG. 10 shows the manner in which FIGS. I1, 12 and 13 can be associated either with FIG. 14 or with FIG. 15,

FIG. 11 is a'schematic diagram of part of the overall circuitry of the said one preferred embodiment of paper currency validator,

FIG. 12 is a schematic diagram of another part of that overall circuitry,

FIG. 13 is a schematic diagram of a further part of that overall circuitry,

FIG. 14 is a schematic diagram of the remaining part of that overall circuitry, and

FIG. 15 is a schematic diagram of a sub-circuit which can be substituted for the sub-circuit shown in FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing in detail, the numeral generally denotes one preferred embodiment of paper currency validator that is made in accordance with the principles and teachings of the present invention. The numeral 32 denotes a platform which extends outwardly from the front of the paper currency validator 30; and that platform will receive the leading edge of each bill which is to be tested by that paper currency validator. Flanges 34 and 36, of generally triangular configuration, extend upwardly from the sides of the platform 32; and that platform has an upwardlyinclined inner end 38 which merges into a platen 40 of rectangular configuration as shown by FIGS. 4 and 5. An elongated flange 42 extends downwardly from each of the elongated sides of the platen 40; and the numeral 44 denotes ears which extend laterally outwardly from the front ends of the flanges 42. The numeral 45 denotes-the trailing edge of the platen 40; and, as indicated by FIGS. 4 and 5, that trailing edge inclines downwardly and then terminates in a verticallydirected lip. As indicated by FIG. 7, the platen 40 has three rectangular slots 46, 48 and 50 in alignment with each other adjacent one side thereof; and that platen has rectangular slots 56, 58 and in alignment with each other adjacent the opposite side thereof. The slot 56 is'in register with the slot 46, the slot 58 is in register with the slot 48, and the slot 60 is in register with the slot 50; and the rear ends of the slots 50 and 60 are cut' away. as shown by FIG. 7. The platen 40 also has a narrow elongated slot-52 therein which has semi-circular ends; and that slot is located between the slots 46 and 56 but is closer to the slot 46 than it is to the slot 56. A similar slot, not shown, also is located between the slots 46 and 56, but it is closer to the slot 56 than it is to the slot 46. The numeral 54 denotes a slot in the platen 40 which is adjacent the trailing edge 45 of that platen; and that slot is closer to the slot 60 than it is to the slot 50. The platen 40 has two additional slots, not shown; and one of those slots accommodates the upper portion of a roller 102 while the other of those slots accommodates the upper portion of a roller 114. Those rollers are indicated by solid lines in FIG. 5 and by dotted lines in FIG. 7.

The numeral 62 denotes a headed pin which has the shank thereof fixedly secured to the left-hand flange 42 of the platen 40, as the paper currency validator is viewed in FIG. 2. As shown by FIGS. 4, 5 and 7, that pin is adjacent the front of that paper currency validator. The numeral 64 denotes an elongated pivot which extends between, and which is supported by openings in, the downwardly-directed flanges 42 on the platen 40; and that pivot is disposed inwardly of the headed pin 62. The numeral 66 denotes a headed pin which can be identical to the headed pin 62, and that headed pin has the shank thereof fixedly secured tothe lefthand flange 42 of the platen 40. The headed pin 66 is close to the rear of the paper currencyvalidator, as shown by FIGS. 4 and 5. A headed pin 68 has the shank thereof secured to the right-hand flange 42 of the platen 40, as the paper currency validator is viewed in FIG. 2; and that headed pin is in register with the headed pin 62. A further headed pin, not shown, is secured to that right-hand flange; and that headed pin is in register with the headed-pin 66.

The numeral 70 denotes a leaf-type spring which is bent so the right-hand end thereof inclines upwardly and to the right in FIG. 4 to bearagainst the under surface of the platen 40. That spring also is bent to have a downwardly-opening saddle, to have an elongated portion which inclines upwardly and to the left in FIG. 7 from that saddle, and to have a bifurcated left-hand end with fingers that define an upwardly-opening saddle. The numerals 72, 74, 76 and 78 denote springs which can be identical to the spring 70; and, as indicated by FIGS. 4 and 5, the spring 72 is adjacent the front of the platen 40 and the spring 74 is adjacent the trailing edge 45 of that platen. The spring 76 is in register with the spring 72, as indicated by FIG. 2; and the spring '78 is in register with the spring 74, as indicated by FIG. 3. A further spring, not shown, is in register with the spring 70. The downwardly-opening saddles of the spring 72, 74 and 76 telescope down over, andare supported by, the headed pins 62, 66 and 68,1'espectively; and the downwardly-opening saddles of the spring 70 and of its counterpart telescope down over,

and are supported by,.the opposite ends of the pivot 64,-

while the downwardly-opening saddle of the spring 78 telescopes down over, and is supported by, the counterpart of headed pin 66. t

A short pivot 80 is supported by the upwardlyopening saddle which is defined by the fingers at the bifurcated end of the spring 72; and that pivot rotatably supports a roller 82. A similar pivot 84 is supported by the upwardly-opening saddle which is defined by the fingers at the bifurcated end of the spring 70; and that pivot rotatably-supports a roller 86. Another similar pivot 88 is supported by the upwardly-opening saddle which is defined by the fingers at the bifurcated end of the spring 74; andthat pivot rotatably supports a roller 90. The numeral 92 denotes a roller which is rotatably mounted on a pivot, not shown,that is supported by the upwardly-opening saddle which is defined by the fingers at the bifurcated end of the spring .76. The numeral 1 93 denotes a roller which is in register with the roller is held by the upwardly-opening saddle which is defined by thefingers at the bifurcated end of the spring 78, as shown by FIG. 3; and a roller 96 is rotatably mounted on that pivot. As shown by FIG. 7, the upper portions of the rollers 82, 86 and are disposed, respectively, within the slots 46, 48 and 50 in the platen 40; and the upper portions of the rollers 92, 93 and 96 are disposed, respectively, within the slots 56, 58 and 60 in that platen. As indicatedby-FIG. 4, the springs 70, 72, 74, 76 and 78 and the spring, not shown, which is the counterpart of spring 70 urge the rollers 86, 82, 90, 92, 96 and 93, respectively, upwardly relative to the platen 40. However, those springs can yield to permit those rollers to be moved downwardly.

The numeral 98 denotes an arm which has a hub that encircles the pivot 64, as indicated by FIG. 8. A pivot 100 is fixedly secured to the outer end of the arm 98, and that pivot rotatably supports the roller 102. As shown by FIG. 9, the opening through that roller has a frusto-conical portion 104 and a frusto-conical portion 106. Those frusto-conical portions enable the roller 102 to tilt relative to the axis of the pivot 100; and a C- washer 103 holds that roller against accidental separation from that pivot. The numeral 110 denotes an arm which has a hub that also encircles the shaft 64; and, as indicated by FIG. 8, the hubs of the arms 98 and 100 confront each other and space those arms apart. A pivot 112 is fixedly secured to the outer end of the arm 110; and that pivot rotatably supports the roller 114. The opening through the roller 114 is defined by two frusto-conical portions in the same manner in which the opening through the roller 102 is defined by two frusto-conical portions. A C-washer 108 is mounted on the pivot 112, and it prevents accidental separation of the roller 114 from that pivot. A torsion spring 116 fill-1 circles the hubs of the arms 98 and 110; and one end of that torsion spring is hooked through an opening in the arm 98, while the other end of that torsion spring is hooked through an opening in the arm 110. Thattorsion spring urges both the roller 102 and the roller 114 upwardly relative to the openings, not shown, which are provided in the platen 40 in register with those r01 lers. However, that torsion spring can yield to permit those rollers to be moved downwardly relative to that platen.

The numeral 118 denotes an upper platen which normally is disposed in parallel relation with, and in close proximity to, the platen 40. The platen 118 has downwardly-directed flanges 120 at its sides thereof; and each of those flanges has a downwardly-opening slot 122 adjacent the forward end thereof. Those slots are dimensioned and disposed to accommodate the outwardly-extending cars 44 at the front ends of the flanges 42 on the lower platen 40. The numeral 124 denotes the semi-cylindrical leading edge of the platen 118; and that semi-cylindrical leading edge is disposed forwardly of the upwardly-inclined rear portion 38 of the platform 32, as indicated by FIGS. 4 and 5. That semi-cylindrical leading edge will coact with the upwardly-inclined rear portion 38 of the platform 32 to provide a desired smoothing and flattening out of any longitudinally-extending wrinkles, creases or folds in bills which are introduced into the paper currency validator 30. The platen 118 has an upwardly-inclined trailing edge 126, as indicated by FIGS. 3-5.

An elongated slot 128 which has semi-circular ends is provided in the platen 118 adjacent one side of that platen; and that slot overlies the rollers 82, 86 and 90. That slot extends from a point which is slightly outward of the roller 82 to a point which is slightly inward of the roller 90. A similar elongated slot 130 is provided in the upper platen 118 adjacent the opposite side of that platen; and that slot overlies the rollers 92, 93 and 96. The slot 130 extends from a point which is slightly outward of the roller 92 to a point which is slightly inward of the roller 96. The numeral 132 denotes a narrow elongated slot in the platen 118 which has the same configuration as the slot 52 in the platen 40; and those slots will be in vertical registry whenever those platens are in the positions shown by FIGS. 4 and 5. The numeral 134 denotes a slot in the platen 118 which is identical to the slot 132; and that slot will be in vertical registry with the slot in the platen 40 which is identical to the slot 52 but which is closer to the slot 56 than it is to the slot 46. The numeral 136 denotes a slot which is generally in registry with the slot 54 in the platen 40; andthat slot is closer to the slot than it is to the slot 128. Two additional slots, not shown, are provided in the platen 118; and one of those slots is in register with the roller 102, while the other of those slots is in register with the roller 114. Those two additional slots are shorter than, but are wider than, the rollers 102 and 114. The platen 118 also has two openings, not shown, which accommodate the lower faces of magnetic heads 208 and 210; and those openings are in register with the rollers 102 and 114. Whenever the platens 40 and 118 are in the positions shown by FIGS. 4 and 5, the torsion spring 116 will urge the upper portions of the rollers 102 and 114 against the air gaps of the magnetic heads 208 and 210, respectively. If, for any reason, the axis of the pivot 100 is not precisely parallel to the air gap of the magnetic head 208, the frusto-conical por tions which define the opening through the roller 102 will enable the portion of that roller which engages that magnetic head to respond to the force which is applied by the spring 116 to move into precise parallelism with that air gap. Similarly if, for any reason, the axis of the pivot 112 is not precisely parallel to the air gap of the magnetic head 210, the frusto-conical portions which define the opening through the roller 114 will enable the portion of that roller which engages that magnetic head to respond to the force which is applied by the spring 116 to move into precise parallelism with that air gap. This is important; because it enables the rollers 102 and 114 to assure full line contact between inserted bills and the air gaps of the magnetic heads 208 and 210 even where a light-pressure torsion spring 116 is used to reduce the resistance which the rollers 102 and 114 will offer to the leading edges of inserted bills.

The numeral 140 denotes a cover for the paper currency validator; and that cover has downwardlydirected flanges 142 at the sides thereof. Each of the flanges 142 has a lateral offset therein, as shown by FIGS. 1-3; and the cover 140 preferably is coextensive with the upper platen 118, as indicated by FIGS. 4 and 5. The numeral 144 denotes a switch bracket which is secured to the cover 140, as shown by FIG. 5; and that switch bracket holds a switch 146 adjacent the front of the platen 118. The numeral 148 denotes a sturdy but thin actuator for the switch 146; and that actuator has a leading edge 150 and a trailing edge 152 which extend downwardly through the slots 132 and 52, respectively, in the platens 118 and 40. As indicated by FIG. 5, the leading edge 150 is essentially straight, and it inclines downwardly from the upper left to the lower right whenever the actuator 148 is in its normal position. The trailing ede 152 is convex, and it inclines downwardly from the upper right to lower left whenever the actuator 148 is in its normal position. The configurations and inclinations of the leading and trailing edges 150 and 152, respectively, of the switch actuator 148 enable the leading edge and trailing edge, respectively, of a bill to engage the leading edge 150 and the trailing edge 152 and easily raise that actuator upwardly out of the slot 52 in the platen 40. As a result,

the switch actuator 148 permits relatively free movement of bills inwardly and outwardly of the paper currency validator 30.

The numeral 154 denotes a second switch bracket which is secured to the cover 140; and that switch bracket supports a switch 156. The numeral 158 denotes the actuator of the switch 156; and that actuator has a convex leading edge 159 which inclines downwardly from upper left to lower right in FIG. 5. That actuator has a trailing edge 16] which is straight and which inclines downwardly from upper right to lower left in FIG. 5. The configurations and inclinations of the leading and trailing edges 159 and 161, respectively, of the switch actuator 158 enable the leading edge and trailing edge, respectively, of a bill to engage the leading edge 159 and the trailing edge 161 and easily raise that actuator upwardly out of the slot in the platen 40 which is in register with the opening 134 in the platen 140. As a result, the actuator 158 permits relatively free movement of bills inwardly and outwardly of the paper currency validator 30.

The numeral 160 denotes a third switch bracket which is secured to the cover 140; and that switch bracket is adjacent the rear of that cover. That switch bracket supports a switch 162; and that switch has an actuator 164 with a leading edge 166 and a trailing edge 168. The leading edge 166 is essentially straight, and it inclines downwardly from upper left to lower right in FIG. and that leading edge will respond to the inward movement ofa bill to, move upwardly out of the slot 54 in the platen 40. The trailing edge 168 of the actuator 164 is generally convex in configuration, but it is quite short; and that trailing edge normally is disposed an appreciable distance below the lower face of the platen 40. As a result, the trailing edge of a bill will not normally engage the trailing edge 168 of the actuator 164 once that trailing edge has moved inwardly beyond that trailingedge of that actuator. If a person were to attempt to pull a bill outwardly of the paper currency validator 30, after the trailing edge of that bill had been moved inwardly beyond the trailing edge 168- of the actuator 164, the trailing edge of that bill would be intercepted by the inner surface of the leading edge 166 of that actuator. In that event, the actuator 164 would make it impossible for that person to recover that bill in intact form.

The numeral 170 denotes a stud-like pivot which has the reduced-diameter outer end thereof fixedly positioned within an opening in one of the flanges 142 of the cover 140. The numerals 172, 178 and 180 denote similar stud-like pivots which have the reduceddiameter outer ends thereof fixedly positioned within openings in the flanges 142. As shown by FIG. 6, the pivots 170 and 178 are in alignment with each other and are close to the front of the paper currency validator 30. The pivots, 172 and 180 are in axial alignment with each other and are spaced a short distance rearwardly of the aligned pivots 170 and 178. The numeral 174 denotes a bushing which is mounted in one of the flanges 142 of the cover 140; and the numeral 176 denotes a further bushing which is mounted in the other flange 142, and that bushing is in axial alignment with the bushing 174. A shaft 182 is rotatably supported by the bushings 174 and 176; and pulleys 192 and 194, which have serrated peripheries, are fixedly secured to that shaft. A pulley 184 is rotatably mounted on the pivot 170; and pulleys 186, 188 and 190 are rotatably mounted, respectively, on'the pivots 172, 178 and 180.

The pulleys 184, 186 and 192 are aligned with each other and are in register with the slot and those pulleys accommodate an elongated endless belt 196 which has an outer surface that provides a high coefficient friction. The pulleys 188, 190 and 194 are aligned with each other and are in register with the slot 128; and those pulleys accommodate an elongated endless belt 198 which has an outer surface that provides a high coefficient of friction. The lower run of the belt 196 is engaged, by the upper portions of the rollers 92, 93 and 96; and the lower run of the belt 198 is engaged by the upper portions of the rollers 82, 86 and 90.

A worm wheel 200 is fixedly secured to the shaft 182; and a worm gear 202 meshes with that worm wheel. That worm gear is mounted on the output shaft 203 of a DC. motor 562 which is enclosed by a motor housing 204. As shown particularly by FIGS. 1 and 3, that motor housing extends upwardly from the cover and it has its axis perpendicular to the central portion of that cover. The motor 562 is a reversible permanent magnet motor which drives an A.C. generator 560 by means of a connection 564.That A.C. generator is located within the motor housing 204; and the connection 564 is a direct mechanical connection. In the said preferred embodiment, the motor 562, the A.C. generator 560 and the connection 564 are parts of a type CYQM Motor With Integral Tachometer Generator which is marketed by the Barber Colman Company as Model No. CYQM 23360-3. When the motor 562 is energized in the forward direction, it will directly drive the A.C. generator 560, and it will drive the lower runs of the belts 196 and 198 inwardly of the papercurrency validator 30. When that motor is energized in the reverse" direction, it will directly drive the A.C. generator 560, and it will drive the lower runs of the belts 196 and 198 outwardly of that paper currency validator.

The numeral 206 denotes a mounting bracket which is shown particularly by FlG.. 7; and that mounting bracket fixedly holds the magnetic heads 208 and 210 in spaced-apart relation. Slots 212 and 214 are provided in that mounting bracket; and the shank of a set screw 216 extends through the-slot 212 to seat within an opening in the platen 118, while the shank of a set screw 218 extends through the slot 214 to seat within a further threaded opening in that platen. By loosening and then re-tightening the set screws 216 and 218, it is possible to adjust the longitudinal position of the mounting bracket 206 relative to the platen 118. This is desirable; because it makes it possible to position the air gaps of the magnetic heads 208 and 210 so they are precisely tangential with the upper surfaces of the rollers 102 and 114, respectively, as indicated by FIG. 5.

It will be'noted that the pulleys 186 and are disposed just a short distance outwardly of the magnetic head 208, as indicated by P16. 5. This is important; because the'leading edge of a well-worn, limp bill,that was being moved inwardly by the belts 196 and 198, might be unable to force the'roller 102 far enough downwardly to pass between that roller and the air gap of that magnetic head. In that event, the belts 196 and 198 would continue to apply inwardly-directed forces to that bill, and would tend to wrinkle and crumple that bill up against the outer face of the magnetic head 208.

If the pulleys 186 and 190 were spaced a considerable distance outwardly of the magnetic head 208, the belts 196 and 198 might be able to move the trailing edge of such a bill well inwardly of the pulleys 186 and 190; and, thereafter when the motor 562 was reversed. the portion of the lower run of the belt 196 which is between the pulleys 186 and 192 and the portion of the lower run of the belt 198 which is between the pulleys 190 and 194 might be unable to apply sufficient pressure to the trailing edge of that bill to cause that bill to move outwardly. However, by disposing the pulleys 186 and 190 just a short distance outwardly of the magnetic head 208, the present invention enables those pulleys to hold the adjacent portions of the lower runs of the belts 196 and 198 in such intimate engagement with the rollers 93 and 86, respectively, that those portions of those belts will fully grip the trailing edge of any wrinkled or crumpled up bill. As a result, the present invention makes certain that the lower runs of the belts 196 and 198 can apply forces to the trailing edge of a wrinkled and crumpled up bill which will enable the reversal of the motor 562 to move that bill outwardly of the paper currency validator 30.

The numeral 220 denotes an elongated pivot which has the opposite ends thereof secured to the rear portions of the flanges 120 on the upper platen 118; and that pivot extends through aligned openings in r the flanges 42 on the lower platen 40, as indicated by FIG. 3. Consequently, the pivot 220 enables the upper platen 118 and the cover 140 plus the various components which are mounted on that upper platen and on that cover to be rotated upwardly and away from the lower platen 40. Such rotation is desirable, because it permits free and ready access to the space between the lower platen 40 and the upper platen 118. However, the-upper platen 118 will normally respond to its weight, to the weight of the cover 140, and to theweight of the components mounted on that upper platen and on that cover to urge the lower face of the lower run of the belt 198 into intimate engagement with the upper faces of the rollers 82, 86 and 90, and also to urge the lower face of the lower run of the belt 196 into intimate engagement with the upper faces of the rollers 92, 93 and 96. The springs 70, 72, 74,76, 78 and the spring, not shown, which is in register with the spring 70 will yield slightly in response to the combined weights of the upper platen 118, of the cover 140, and of the components which are carried by that upper platen and by that cover; but those springs will hold the upper surfaces of the rollers 86, 82,90, 92, 96 and 93, respectively, above the upper surface of the lower platen 40, as shown by FIG. 4.

Referring particularly to FIG. 11, the numeral 230 denotes a conductor which is connected to the positive terminal of an unregulated source of thirty volts DC. by a conductor 232; and the numeral 234 denotes a further conductor which is connected to that positive terminal by a conductor 236. The numeral 238 denotes a conductor which serves as a ground for the sub-circuit in FIG. 11; and the numeral 240 denotes a filter capacitor which is connected between the conductor 230 and the grounded conductor 238.

Each of the magnetic heads 208 and 210 has one terminal thereof connected to the grounded conductor 238. The other terminal of the magnetic head 208 is connected to the conductor 230 by a constant current diode 242 of standard and usual design; and the other terminal of the magnetic head 210 is connected to the conductor 234 by a similar constant current diode 244. Those constant current diodes permit a predetermined amount of direct current to flow through the coils of those magnetic heads, and thereby enable those mag netic heads to operate as biased magnetic heads.

The numeral 246 denotes an Amplifier which includes an NPN transistor 248, an NPN transistor 250, resistors 252, 254, 256 and 258, capacitors 260, 262, 264 and 266, and a diode 268. The capacitor 260 couples the output of the magnetic head 208 to the base of transistor 248; and the output of that transistor is di rectly coupled to the base of the transistor 250. The numeral 270 denotes an Amplifier which is shown as being identical to the Amplifier 246; and the counterpart of capacitor 260 couples the output of magnetic head 210 to the base of the counterpart of transistor 248. While the Amplifiers 246 and 270 are very useful and desirable, any suitable high quality amplifiers of comparable nature could be substituted for them.

The numeral 272 denotes a Squaring Circuit which includes an NPN transistor 274 and an inverter 276. The capacitor 266 couples the output of Amplifier 246 to the base of transistor 274; and the inverter 276 inverts the output of transistor 274 and couples it to a Frequency-Sensing Circuit 280. The numeral 278 denotes a Squaring Circuit which is identical to the Squaring Circuit 272; and the inverter in the Squaring Circuit 278 couples the output of the transistor of that Squaring Circuit to a Frequency-Sensing Circuit 292.

The Frequency-Sensing Circuit 280 includes a fixed inductor 282, fixed capacitors 284 and 286, a resistor 288, and a diode 290. The capacitors284 and 286 coact with the inductor 282 to constitute a tuned circuit that has a center frequency of approximately 1,150 Hertz. The resistor 288 couples the output of the Squaring Circuit 272 to that tuned circuit; and the diode 290 couples the output of that tuned circuit to a Threshhold Detector 294.

The Frequency-Sensing Circuit 292 is shown as being identical to the Frequency-Sensing Circuit 280; and it has a fixed inductor, two fixed capacitors a resistor, and a diode. That resistor couples the output of the Squaring Circuit 278 to the tuned circuit of the Frequency- Sensing Circuit 292; and that diode couples the output of that tuned circuit to a Threshhold Detector 308.

The Threshhold Detector 294 includes NPN transistors 296 and 298, a diode 300, a capacitor 302, and resistors 304 and 306. The Threshhold Detector 308 includes NPN transistors 297 and 299, a diode 301, a capacitor 303, and resistors 305 and 307.

The numeral 310 denotes a Validation Latch Circuit which includes NAND gates 312 and 314, an inverter 316, and a conductor 318 which extends from the output of the inverter 316 to a conductor 319 which interconnects the lower input of NAND gate 312 and the upper input of NAND gate 314. The numeral 320 denotes a diode which has the anode thereof connected to the junction of resistors 304 and 306, and which has the cathode thereof connected to the cathode of a diode 322 and also a conductor 328. That conductor extends through FIGS. 12 and 13 and into FIG. 14. The diode 322 has the anode thereof connected to the junction of resistors 305 and 307.'The numeral 326 denotes a conductor which extends from the output of inverter 316 through FIG. 12 into FIG. 13. The numeral 324 denotes a conductor which is connected to the outputs of NAND gates 312 and 314; and that conductor extends through FIG. 12 into FIG. 13. A conductor 325 extends from the conductor 324 in FIG. 11 into FIG. 12.

Referring particularly to FIG. 12, the numeral 329 denotes a Start Switch Circuit which includes the switch 146, a resistor 330, an NPN transistor 332 and a resistor338. The resistor 330 connects the collector of transistor 332 to the positive terminal of a regulated source of 15 volts DC. The numeral 339 denotes a Sequence Switch Circuit which includes the switch 156,

' a resistor 340, an NPN transistor 342, and a resistor 346. The resistor 340 connects the collector of transistor 342 to the positive terminal of the regulated source of 15 volts DC. The numeral 349 denotes an Exit Switch Circuit which includes the switch 162, a resistor 348, an NPN transistor 350, and a resistor 354. The resistor 348 connects the collector of transistor 350 to the positive terminal of the regulated source of 15 volts D.C.

The collector of transistor 332 is connected to the upper input of a NAND gate 334, and also to a conductor 336 which extends into FIG. 13. The collector of transistor 342 is connected to the middle input of NAND gate 334, and also to a conductor 344 which extends into FIG. 13. The collector of transistor 350 is connected to the lower input of NAND gate 334, and also to a conductor 352 which extends into FIG. 13.

The numeral 356 denotes a Vend Circuit which includes a NAND gate 358, an inverter 360, a resistor 362, an NPN transistor 364 which is connected as an 8.2 volt Zener diode, an NPN transistor 366, a relay coil 368 and a diode 370 which are connected in parallel with each other, and normally-open relay contacts 372. The lower terminal of coil 368 and the anode of diode 370 are connected to the collector of transistor 366; and the upper terminal of that coil and the cathode of that diode are connected to the positive terminal of the source of unregulated thirty volts DC. The relay coil 368 controls the normally-open relay contacts 372;

and conductors 374 and 376 extend from those relay contacts to the terminals of a vending machine, not shown. That vending machine could be a change maker. a product vendor 'or a vendor of services with which the paper currency validator 30 is used.

The numeral 378 denotes a conductor which extends from the output of the inverter 360 to the input of an inverter 380. The output of the latter inverter is connected to the bases of the transistors 332, 342 and 350 by the resistors 338, 346 and 354, respectively.

The numeral-382 denotes a VentTime Circuit which includes a diode 384, a resistor 386, a capacitor 388,

an NPN transistor 392 which is connected as an 8.2,

418 and 420. A conductor 414 connects the collector of transistor 402 and the upper terminal of resistor 420 to the positive terminal of the source of regulated 15 volts D.C. Resistors 416 and 418 connect the emitter of transistor 402 to ground; and the junction of those resistors is connected to the base of transistor 404. The lower terminal of resistor 420 is connected to the collector of transistor 404 and to the base of transistor 406. A conductor 422 extends from the collector of transistor 406 through FIG. 13 into FIG. 14.

The numeral 424 denotes a conductor which extends from the output of NAND gate 334 to the upper terminal of capacitor 408 in the Gross Time Delay Circuit 400 and then into FIG. 13. An inverter 426 connects the output of NAND gate 334 to the lower input of NAND gate 358 in the Vent Circuit 356. The upper input of NAND gate 358 is connected to the conductor volt Zener diode, resistors 394 and 396, and an NPN transistor 398. The cathode of diode 384 is directly connected to the conductor 352. The lower terminals of resistor 386 and of capacitor 388 are connected immediate the anode of diode 384 and the emitter of transistor 392; and the upper terminals of that resistor and of that capacitor are connected to the positive terminal of the source of regulated 15 volts DC. by a conductor 390. The emitter of transistor 398 is connected to ground, the collector of that transistor is connected to conductor 325, and the base of that transistor is connected to the junction of resistors 394 and 396.

The numeral 400 denotes a Gross Time Delay Circuit which includes NPN transistors 402, 404 and 406, capacitors 408 and 410, a diode 412', and resistors 416,

Referring particularly to FIG. 13, the numeral 428 denotes a Positional Time Delay Circuit which includes an inverter 430, diodes 432 and 434, a resistor 436, a capacitor 440, and an NPN transistor 442 which is connected as a 8.2 voltZener diode. A conductor 438 connects the upper terminal of the resistor 436 and hence the anodes of diodes 432 and 434, the upper terminal of capacitor 440, and the emitter of transistor 442 to the positive terminal of the source of regulated 15 volts DC. The cathode of diode 432 is connected to conductor 352, and the input of inverter 430 is connected to conductor 344.

The numeral 444 denotes a Further Time Delay Circuit which includes an inverter 446, diodes 448 and 450, a capacitor 452, a resistor 454, and an NPN transistor 458 which is connected as a 8.2 volt Zener diode.- A conductor 456 connects the upper terminal of the resistor 454 and hence the anodes of diodes 448 and 450,-theuppe'r terminal of capacitor 452, and the emitter of transistor 458 -'to the positive terminal of the source of regulated 15 volts DC. The cathode of diode 448 is connected to conductor 326, and the input of inverter 446 is connected to conductor 352.

The numeral 460 denotes a Time Delay Output Circuit which includes an NPN transistor 462 and a resistor 464. The collectors of the NPN transistors 442 and 458 are connected to the upper terminal of resistor 464 and to the base of transistor 462. The lower terminal of the relay coil 468; and the upper'terminal of that relay coil and the cathode of that diode are connected to the positive terminal of the source of unregulated thirty volts DC. The lower terminal of that relay coil and the anode of that diode are connected to the collector of an NPN transistor 476 which has the emitter thereof connected to ground by a resistor 478. A resistor 480 and a Zener diode 482 are connected as a voltage divider; and the junction between that resistor and that Zener diode is connected to the base of transistor 476.

The anode of the Zener diode 482 is grounded.

494. Those diodes have the anodes thereof connected together and to the input of the inverter 488. An inverter 484 connects the conductor 336 to the cathode of diode 490, and also to the upper input of a NAND gate 506 in a Bill Retrieval Circuit 504. The cathode of diode 492 is connected to conductor 344, and the cathode of diode 494 is connected to the output of inverter 446 in the Further Time Delay Circuit 444.

The numeral 496 denotes a Short Paper Circuit which includes a NAND gate 498 and diodes 500 and 502. Those diodes have the anodes thereof connected together and to the lower input of that NAND gate. The upper input of NAND gate 498 is connected to the conductor 336; and the output of that NAND gate is connected to the conductor 463. The cathode of diode 500 is connected to the output of inverter 430, and the cathode of diode 502 is connected to the conductor 352.

The middle input of the NAND gate 506 in the Bill Retrieval Circuit 504 is connected to the conductor 352; and the lower input of that NAND gate is connected to the conductor 324. The output of that NAND gate is connected to the conductor 463.

The numeral 508 denotes a Switch-Checking Circuit which includes a NAND gate 510', and the upper input of that NAND gate is connected to the conductor 336, while the lower input of that NAND gate is connected to the conductor 326. The middle input of the NAND gate 510 is connected to the output of the inverter 446 in the Further Time Delay Circuit 444, and the output of that NAND gate is connected to the conductor 463.

The numeral 512 denotes a Line Cording Circuit which includes a resistor 514 and a capacitor 516. The lower terminals of that resistor and of that capacitor are grounded, and the upper terminals of that resistor and of that capacitor are connected to the conductor 463.

The numeral 518 denotes a Reverse Relay Latch Circuit which includes inverters 520 and 522 and diodes 524 and 526. The input of inverter 520 and the anode of diode 524 are connected to the conductor 463; and the output of that inverter and the cathode of diode 526 are connected together and'to the upper terminal of resistor 480 in the Motor Reverse Circuit 466. A diode 528 connects the conductor 324 and to the cathode of diode 524 and to the output of inverter 522; and a diode 532 has the cathode thereof connected to the conductor 424, and has the anode thereof connected to the input of inverter 522 and to the anode of diode 526.

The numeral 530 denotes a diode which has the cathode thereof connected to the output of inverter 488 in the Tail Gate Circuit 486. The anode of that diode is connected to the conductor 463.

Referring particularly to H6. 14, the numeral 533 denotes an Amplitude-Responsive Control Circuit which includes an integrated circuit 534, NPN transistors 538 and 554, resistors 542, 546, 552, 556 and 558, a potentiometer 544, a capacitor 548, and a diode 550. While various integrated circuits could be used as the integrated circuit 534, the said preferred embodiment of paper currency validator uses a Motorola MC 1723- C L Voltage Regulator as that integrated circuit.

A conductor 536 connects pins 11 and 12 of the integrated circuit 534 to the positive terminal of the source of regulated fifteen volts DC; and pins 3 and 7 of that integrated circuit are grounded. Pins Stand 6 of the integrated circuit 534 are connected together; and pin 4 of that integrated circuit is connected to the movable contact of the potentiometer 544. The conductor 422 is connected to pin 13 of the integrated circuit 534, and pin 9 of that integrated circuit is connected to the base of transistor 554 by the resistor 552. Pin 2 of the integrated circuit 534 is connected to the junction of resis tors 556 and 558. A conductor 540 connects the collector of transistor 538 to the positive terminal of the source of regulated 15 volts DC. The lower terminals of resistor 558 and of capacitor 548 are grounded. The resistor 542, the potentiometer 544 and the resistor 546 are connected in series between the emitter of transistor 538 and ground.

The motor housing 204 is denoted in FIG. 14 by a dashed-line block; and that motor housing encloses the AC. generator 560, the DC. motor 562, and the driving connection 564. In the said preferred embodiment, a DC. motor is selected which will produce a minimum of electrical noise resulting from the interaction between the brushes and the commutator thereof, because any such electrical noise would adversely affect the operation of the Frequency-Sensing Circuits 280 and 292, and could adversely affect the operation of other circuits of that preferred embodiment. However, the electrical noise from even the least noisy commercially-available, reversible, adjustable-speed DC. motor is great enough to adversely affect the operation of the Frequency-Sensing Circuits 280 and 292; and hence a capacitor 566'is connected between the upper terminal of the motor 562 and the motor housing 204, and a capacitor 568 is connected between the upper and lower terminals of that motor. Those capacitors will effectively attenuate the electrical noise developed by the motor 562, and will thereby keep that electrical noise from affecting the operation of any other component or sub-circuit of the paper currency validator 30.

The upper terminal of the motor 562 is connected to the left-hand stationary relay contact 470, and also to the stationary right-hand relay contact 472. The lower terminal of that motor is connected to the left-hand stationary relay contact 472, and also to the stationary right-hand relay contact 470. The movable relay contact 470 is connected to the positive terminal of the source of unregulated 30 volts DC. by a conductor 569. The movable relay contact 472 is connected to the collector of the transistor 554; and a diode 570 has the anode thereof connected to the movable relay contact 472, and has the cathode thereof connected to the movable rela'y contact 470. That diode will provide a discharge path for the inductive energy within the motor 562 whenever the current flowing through that motor is interrupted. The numeral 572 denotes a Current-Sensing Circuit which includes a differential amplifier 574, a potentiometer 580, resistors 578 and 582, and an inverter 586. One terminal of that differential amplifier is connected to ground, and another terminal of that differential amplifier is connected to the positive terminal of the source of regulated 15 volts DC. by a conductor 576. The resistor 578, the potentiometerSSO, and the resistor 582 are connected between ground and a conductor 584 which extends to the positive terminal of the source of regulated 15 volts D.C.

The movable contact of the potentiometer 580 is connected to the lower input terminal of the differential amplifier 574; and the emitter of that transistor 554 is connected to the upper input terminal of thatdifferential amplifier. The input of the inverter 586 is connected to the output of the differential amplifier 574; and the output of that inverter is connected to the conductor. 328.

Referring particularly to FIG. 15, the numeral 588 denotes a Frequency-Responsive Control Circuit which can be substituted for the Amplitude-Responsive Control Circuit 533 of FIG. 14. That Frequency- Responsive Control Circuit is not, per se, a part of the present'invention; and it is disclosed herein solely to illustrate the adaptability of the circuitry of FIGS. 11-13 to various speed-regulating control systems. That Frequency-Responsive Control Circuit includes NPN transistors 590, 624, 630 and 670, resistors 592, 594, 602, 614, 622, 626, 632, 634, 636', 638, 644, 648, 664, 666, 668, 672 and 674, diodes 598 and 656, a stable, nonretriggering one-shot 606, a potentiometer 646, capacitors 600, 608, 610, 616, 640, 642, 658 and 660, an inverter 620, and an operational amplifier 650. A conductor 596 connects the upper terminal of resistor 594 to the positive terminal of the source of regulated 15 volts D.C., and the left-hand terminal of resistor 592 is connected to the un-grounded output terminal of the A.C. generator 560. The diode 598 has the anode thereof grounded, and has the cathode thereof connected between resistor 592 and the base of transistor 590. The emitter of transistor 590 is grounded, and the collector-of that transistor is connected to the lower terminal of resistor 594. I v

The resistor 602 has the lower terminal thereof connected between the capacitor 600 and pin 2 of the oneshot 606; and the upper terminal of that resistor is connected to the positive terminal of the source of regulated l volts DC. by a-conductor 604. That capacitor and that resistor constitute a differentiator; and the output of that differentiator is applied topin 2 of the one-shot 606. That one-shot will change the state of the output at pin 3 thereof only when a negative-going signal is applied to the pin 2.

The capacitor 608 connects pin 4 of the one-shot 606 to ground. and the capacitor 610 connects pin 5 of that one-shot to ground. A conductor 612 connects pin 8 of the one-shot 606 to the positive terminal of the source of regulated volts DC; and the resistor 614 has the upper terminal thereof connected to that positive terminal by aconductor 618. The capacitor 616 connects the lower terminal of resistor 614 to ground; and the junction between that resistor and that capacitor is connected to pins 6 and 7 of the one-shot 606.

The inverter 620 has the input thereof connected to I the conductor 422, and has the output thereof connected to the base of transistor 624 by the resistor 622. The resistor 626 has the upper terminal thereof connected to the positive terminal of the source of regulated I5 volts DC. by a conductor 628; and the lower terminal of that resistor is connected to the collector of transistor 624, to the collector of transistor 630, to the upper terminal of resistor 634, and to the left-hand terminal of resistor636. The emitter of transistor 630 is grounded, and the base of that transistor is connected to the pin 3 of the one-shot 606 by the resistor 632. The right-hand terminal of resistor 636 is connected to the upper terminal of resistor 638, to the upper terminal of capacitor 642, and to the upper input of operational amplifier 650. The lower terminal of resistor 638 is connected to ground by the capacitor 640.

Resistor 644 has the upper terminal thereof connected'to the positive terminal of the source of regulated 15 volts DC; and the lower terminal of that resistor is connected to the upper terminal of potentiometer 646 which has the lower terminal thereof connected to ground by resistor 648. Resistor 664 connects the movable contact of potentiometer 646 to the lower input of operational amplifier 650; and one terminal of that operational amplifier is connected to the positive terminal of the source of regulated 15 volts DC. by a conductor 652, while another terminal of that operational amplifier is connected to the negative terminal of that source of regulated 15 volts DC. by a conductor 654. The upper terminals of resistor 633 and of capacitor 642 are connected to the upper input of operational amplifier 650. The diode 656 has the anode thereof connected to the output of operational amplifier 650, and has the cathode thereof connected to the base of tran' sistor 670.by the resistor 666. The capacitor 658 and the series-connected capacitor 660 and resistor 662 constitute feed back paths from the cathode of diode 656 to the lower input of, operational amplifier 650. The resistor 668 is connected between ground and the right-hand terminal of resistor 666 and the base of transistor 670; and resistors 672 and 674 are connected in series between the emitter of that transistor and ground. That emitter is connected to the upper input of the differential amplifier 574 of a Current-Sensing Circuit 572 which is identical to the similarly-numbered Current-Sensing Circuit of FIG. 14. The collector of transistor 670 is connected to movable relay contact 472 and to the anode of diode 570; and that movable relay contact, that diode, the other relay contacts 472, the relay contacts 470, the motor 562, the motor housing 204, the AC. generator 560, the connection 564, the capacitors 566 and 568, and the conductor 569 of FIG. 15 are identical to the similarly-numbered elements in FIG. 14. Effectively, the sub-circuit of FIG. 15

is the same asthe sub-circuit of FIG. 14 except forthe substitution of the Frequency-Responsive Control Circuit 588 for the Amplitude-Responsive Control Circuit 533 of FIG. 14. v v

The values of capacitors 658 and 660 and the value of resistor 662 are selected to make the sub-circuit of FIG. 15 operate as a second order system. Such a system is a slightly underdamped system; and hence it will permit a very small amount of overshooting to occur thereby enabling that sub-circuit to provide a desirably rapid response.

In the said preferred embodiment, some of the NAND gates are portions of integrated circuits, and some of the inverters are parts of integrated circuits.

For example, the NAND gates 312 and 314 of FIG. 11,

the NAND gate 358 in FIG. 12, and the NAND gate 498 in FIG. 13 are parts of a quad 2-input NAND gate which is identified as Motorola MC 668. The NAND gate 334 in FIG. 12 and the NAND gates 506 and 510 in FIG. 13 are parts of a three3-input NAND gate which is identified as Motorola MC 670. The inverter 276 and its counterpart in FIG. 11, and the inverters 430, 446, 484 and 488 in FIG. 13 are parts of a hex inverter which is identified as Motorola MC 680; and the inverter 316 in FIG. 11, the inverters360, 380- and 426 in FIG. 12, and the inverters 520 and 522 in FIG. 13 are parts of another hex inverter which is identified as Motorola 'MC 680.

The differential amplifier 574 in F168. 14 and can be an operational amplifier which is identified as Motorola MC 174 l-CP l. The one-shot 606 in FIG. 15 can be a timer which is identified as Signetics NE 555V. The operational amplifier 650 in FIG. 15 can be an operational amplifier which is identified as Motorola MC 1741-CP l. The other components of FIGS. 11-15 can bestandard and usual commercial grade components.

In the said preferred embodiment, the length of the lower platen 40 is shorter than the length of a U.S. dollar bill. Specifically, the distance from the rear edge of the upwardly-inclined inner end 38 of the platform 32 to the rear of the downwardly-inclined trailing edge 45 of the lower platen 40 is about 5 -7/ 16 inches, whereas the average length of a U.S. dollar bill is about 6- /8 inches. The upper platen 118 is slightly longer than the lower platen 40, as indicated by F168. 4 and 5; and the distance from a vertical projection of the front of the semi-cylindrical leading edge 124 Ma vertical projection of the rear of the trailing edge 126 is just slightly less than 6 inches. Consequently, the upper platen 118 also is shorter than a U.S. dollar bill. The distance between the downwardly-directed flanges 120 at the sides of the upper platen 118 is slightly greater than the width ofa U.S. dollar bill; and hence such a bill can easily be moved inwardly of the space defined by the lower platen 40, the upper platen 118, and the flanges 120 on that upper platen.

The outer end of the slot 52 in the lower platen 40 is located about eleven-sixteenths of an inch inwardly of the rear edge of the upwardly-inclined inner end of the platform 32; and the outer end of the slot. not shown. in that platen, which is in register with the slot 134 in the platen 118. is located about fifteensixteenths of an inch inwardly of that rear edge of that upwardly-inclined inner end. Each of those slots is approximately 1 Vs of an inch long and approximately oneeighth of an inch wide. The outer end of the slot 54 in the platen 40 is located about 1% inches outwardly of the rear of the downwardly-inclined trailing edge 45 of that platen; and that slot is approximately fifteensixteenths of an inch long and approximately fivesixteenths of an inch wide.

The outer end of each of the slots 46 and 56 in the platen 40 is located about 1 inch inwardly of the rear edge ofthe upwardly-inclined inner end 38 of the platform 32; and each of those slots is about one-half of an inch long and about nine thirty-seconds of an inch wide. The distance between the inner edge of slot 46 and the outer edge of the slot 48 is about one-half of an inch; and, similarly. the distance between the confronting edges of the slots 56 and 58 is about one-half of an inch. Each of the slots 48 and 58 is about one-half of an inch long and about nine thirty-seconds of an inch wide. The distance between the confronting edges of the slots 48 and 50 is about 2-1/3?. of an inch; and, similarly, the distance between the confronting edges of the slots 58 and 60 is about 2-1/32 of an inch. The outer edge of the slot, not shown, which receives the roller 102 is located about 2% inches inwardly of the rear edge of the upwardly-inclined inner end 38 of the platform 32; and the outer edge of the slot, not shown, which accommodates the roller 114 is located about seven-sixteenths of an inch inwardly of the inner edge of the slot which accommodates the roller 102.

The switch actuator 148 is located so the leading edge of a bill must be moved about l-5/l6 of an inch inwardly of a vertical projection of the front of the semi-cylindrical leading edge 124 of platen 118 before it moves that switch actuator far enough to close switch 146. The leading edge of that bill must be moved about three-eighths of an inch further inwardly before it can engage the lower runs of belts 196 and 198. After the leading edge of that bill has been moved inwardly of the vertical projection of the front of the semi-circular leading edge 124 of platen 118 a total distance of about l-l3/l6 of an inch, that leading edge will cause the switch actuator 158 to close the switch 156. Not until the leading edge of the bill has been moved a total distance of approximately 4-15/16 of an inch inwardly of the vertical projection of the front of the semicylindrical leading edge 124 of the upper platen 118 will that leading edge cause the switch actuator 164 to close the switch 162.

The air gap of the magnetic head 208 is located about 3-3/16 of an inch inwardly of the front of the semicylindrical leading edge 124 of the upper platen 118; and the air gap of the magnetic head 210 is located about 1 inch further inwardly. The leading edge of the ovate portrait background on a U.S. dollar bill will not move into register with the air gap of the magnetic head 208 until the leading edge of that bill has caused the switch actuator 164 to close the switch 162, and then has been moved approximately three-quarters of an inch further inwardly.

The leading edge of the inserted bill must be moved 1 approximately 4-3/16 of an inch, after it has caused the actuator 158 to close the switch 156, before that leading edge can cause the actuator 164 to close the switch 162. Furthermore, the bill must be moved approxi mately 1% of an inch further inwardly of the paper currency validator 30, after the leading edge of that bill has caused the actuator 164 to close the switch 162, before the vertical grid lines in the leading half of the portrait background can engage the air gap of the magnetic head 210 and the vertical grid lines in the trailing half of that portrait background can engage the air gap of the magnetic head 208.

The motor 562 will drive the pulleys 192 and 194 by means of its output shaft 203, worm gear 202, worm wheel 200, and the shaft 182. That motor will drive the pulleys 19 2 and 194 at a speed which will make the linear speed of each of the belts between 9-1/10 and 9-5/ 10 of an inch per second. Those belts will cause an inserted bill to move at that same speed; and hence that bill will move inwardly at a rate between 94/10 and 9-5/10 of an inch per second. This means that it will take an inserted bill approximately 450 milliseconds to move from the position wherein it effects closure of the switch 156 to the position wherein it effects closure of the switch 162. Thereafter, it will take that bill approximately 188 milliseconds to move from the position wherein it effects closure of the switch 162 to the position wherein the air gaps of both magnetic heads 208 and 210 should sense vertical grid lines in the portrait background. Those vertical grid lines will move past those air gaps at a rate of approximately 1 times a second.

Whenever the paper currency validator.30 is in its standby condition, the switches 146, 156 and 162 will be open, as shown by FIG. 12. As a result, all of the transistors 332, 342, 350 will be non-conductive; and essentially l5 volts will appear at the collectors of each of those transistors. That voltage will constitute a logic l whereas ground voltage will constitutea logic 0. This means that in the standby condition of the paper 4 currency validator 30, logic I will appear at all of the inputs of the NAND gate 334, at the input of inverter 484 in FIG. 13, at the upper input of NAND gate 498 in FIG. 13, and at the upper input of NAND gate 510 in FIG. 13. Additionally, logic I will appear at the input of inverter 430 in FIG. 13 and at the cathode of diode 492 in FIG. 13. Further, logic I will appear at the cathode of diode 384 in FIG. 12, at the cathode of diode 432 in FIG. 13, at the input of inverter 446 in FIG. 13, at the cathode of diode 502 in FIG. 13, and at the mid dle input of NAND gate 506 in FIG. 13. The output of NAND gate 334 in FIG. 12 will be logic 0; and hence the transistor 402 in the Gross Time Delay Circuit 400 of FIG. 12 will be non-conductive and the transistor 404 in that circuit also will be non-conductive. Howlogic 0 to the base of transistor 554. This means that the motor 562 will be de-energized, and the belts 196 and 198 will be stationary. At this time, logic 0 will appear at pin 2 of the voltage regulator 534; and logic 0 will appear at the movable contact of potentiometer 544 and hence at pin 4 of that voltage regulator.

The magnetic heads 208 and 210 will have DC biasing currents flowing through them; but those magnetic heads will not supply any signals, to the capacitor 260 in the Amplifier 246 or to the counterpart capacitor in the Amplifier 270, which could be amplified by those Amplifiers. As a result, the transistors 296- and 297 in the Threshold Detectors 294 and 308 will be nonconductive; and hence the collector of transistor 298 will apply logic I to the upper input of NAND gate 312, while the collector of transistor 299 will apply logic I to the lower input of NAND gate 314, If, at the time the paper currency validator 30 was connected to the sources of regulated l5 volts D.C. andof unregulated 30 volts DC, the voltage at the lower input of NAND gate 312 had been logic 0, logic I would have appeared at the output of that NAND gate; and that logic I would have. been applied by the conductors 324 and 325 to the collector of transistor 398 in FIG. 12. Because the diode 384 would have had logic I at the cathode thereof, that diode would have been back-biased; and hence parallel connected resistor 386 and capacitor 388, transistor 392, and resistors 394 and 396 would have applied a positive voltage to the base of transistor 398 which would have rendered that transistor conductive. Thereupon, that transistor would have provided a logic 0 on the conductors 325 and 324, and thus at the input of inverter 316; and that inverter would have applied logic I to the lower input of NAND gate 312 and to the upper input of NAND gate 314. Those NAND gates would then have provided logic 0 on conductors 324 and 325 and at the input of inverter 316; and that inverter would thereafter have maintained logic I at the lower input of NAND gate 312, at the-upper'input of NAND gate 314, at the cathode of diode 448 in FIG. 13, and at the lower input of NAND would have back-biased the diode 528 and would have appeared at the lower input of NAND gate 506; and the logic 0 on the conductor 325 would have rendered the transistor 398 non-conductive. The conductor 325 is considered to be the validation line of the paper currency validator 30; and the logic. 0 on that conductor during the standby condition of that papercurrency validator means that no validation signal is present during that standby condition.

The logic 0 on the conductor 325 will be applied to the upper input of NAND gate 358; and the resulting logic I at the output of that NAND gate will cause the inverter 360 to apply logic 0 to the base of-transistor 366 and to the input of inverter 380. Transistor 366 will respond to the logic 0 at the base thereof to be nonconductive; and hence the vend relay coil 368 will be de-energized and will leave the relay contacts 372 open. This means that the Vend Circuit 356 will not be supplying a vend signal during the standby condition of the paper currency validator 30.

The logic 0 at the input of inverter 380 will cause that inverter to apply logic I to the base of each of the transistors 332, 342 and 350 in FIG. 12. However, all of those transistors will be non-conductive, because the emitters thereof are disconnected from ground by the open switches 146, 156 and 162. g

The inverter 430 in FIG. 13 will respond to the logic I at the input thereof to apply logic 0 to the cathode of diode 434 and to the cathode of diode 500. The diode 434 will thus be forward-biased; and it will apply logic 0 to the upper terminal of capacitor 440 and'to the emitter of transistor 442, thereby keeping that transistor from applying a positive voltage to the base of transistor 462. The inverter 446 in FIG. 13 will respond to the logic I at the input thereof to apply logic 0 to the,

cathode of diode "450, to the cathode'of diode 494,9and to the middle input of NAND gate 510. The diode 450 will thus be forward-biased; and it will apply logic 0 to the upper terminal of capacitor 452 and to the emitter The logic I at the cathode of diode 432 will back-bias that diode; but the forward-biased diode 434 will keep logic 0 on the upper terminal of capacitor 440 and at the emitter of transistor 442. Similarly, the logic I at the cathode of diode'448 will back-bias that diode; but

the forward-biased diode 450 will keep logic O-on the upper terminal of capacitor 452 and at the emitter of transistor 458.'Consequently, as indicated hereinbefore, the transistor 462 will be non-conductive and will provide logic I on the conductor 463.

The inverter 484 in FIG. 13 will respond to the logic 1 at the input thereof to apply logic 0 to the cathode of diode 490 and also to the upper input of NAND gate 506. The logic I at the cathode of diode 492 in FIG. 13 will back-bias that diode; but the logic 0 at the cathodes of the diodes 490 and 494 will forwardbias those diodes thus causing those diodes to apply logic 0 to the input of inverter 488. The resulting logic I at the output of that inverter will back-bias the diode 530 

1. A validator which comprises a sensing element, means to provide relative movement between an authentic document and said sensing element to develop a signal having a given frequency, and a frequency-sensing circuit which has the essential elements thereof fixed in nature rather than adjustable in nature, whereby said frequency-sensing circuit has greater stability and is less expensive than a comparable frequency-sensing circuit which has the essential elements thereof adjustable in nature, said essential elements of said frequency-sensing circuit helping establish and maintain a predetermined center frequency for said frequency-sensing circuit, and said means having a speedadjusting sub-circuit which permits the rate of said relative movement to be adjusted to cause said given frequency of said signal to be sufficiently close to said predetermined center frequency to enable said frequency-sensing circuit to respond to said signal.
 2. A validator as claimed in claim 1 wherein said means includes an adjustable speed D.C. motor and a feedback loop that keeps the adjusted speed of said D.C. motor substantially constant.
 3. A validator as claimed in claim 1 wherein said means includes an adjustable speed D.C. motor and an amplitude-responsive control circuit which is part of a feedback loop that keeps the adjusted speed of said D.C. motor substantially constant, and wherein a feedback generator supplies feedback to said amplitude-responsive control circuit which has an amplitude that varies with the speed of said D.C. motor.
 4. A validator as claimed in claim 1 wherein said means includes an adjustable speed D.C. motor and an amplitude-responsive control circuit which is part of a feedback loop that keeps the adjusted speed of said D.C. motor substantially constant, wherein a feedback generator supplies feedback to said amplitude-responsive control circuit which has an amplitude that varies with the speed of said D.C. motor, wherein said speed-adjusting sub-circuit includes an adjustable impedance to adjust the effective value of said feedback, and wherein said speed-adjusting sub-circuit develops a reference and compares said effective value of said feedback with said reference to produce an error signal which is proportional to any variation between the actual speed and the desired speed of said D.C. motor.
 5. A validator as claimed in claim 1 wherein one of said essential elements of said frequency-sensing circuit is a fixed value inductor, wherein another of said essential elements of said frequency-sensing circuit is a fixed value capacitor, and wherein said fixed value inductor and said fixed value capacitor are components of a tuned circuit.
 6. A validator which comprises document-moving members that move a document inwardly of said validator, a sensing device that responds to the inward movement of an authentic document relative thereto by said document-moving members to develop a signal, position-sensing means that responds to a document and that senses when said document-moving members move a document inwardly to a predetermined position within said paper currency validator, a timing circuit that responds to the sensing by said position-sensing means of the inward movement of a document to initiate a time period of predetermined duration, and means to reverse the direction of movement of said document-moving members and thereby move said document outwardly of said validator if said sensing device does not develop said signal before the end of said time period.
 7. A validator as claimed in claim 6 wherein said position-sensing means senses the inward movement of the leading edge of said document and wherein said sensing device senses a portion of said document which is located reArwardly of said leading edge of said document.
 8. A validator as claimed in claim 6 wherein said timing circuit includes a capacitor which experiences a given change in the charge therein during said time period, and wherein an opposite change in said charge in said capacitor occurs, when said sensing device develops said signal, to keep said means from reversing the direction of movement of said document-moving members.
 9. A validator as claimed in claim 6 wherein said timing circuit includes a capacitor which experiences a given change in the charge therein during said time period, wherein an opposite change in said charge in said capacitor occurs, when said sensing device develops said signal, to keep said means from reversing the direction of movement of said document-moving members, wherein said means includes a control element with a threshold level, and wherein said means includes a Zener device that requires the voltage across said capacitor to exceed said threshold level of said control element by a fixed amount before said control element can be actuated.
 10. A validator which comprises a sensing element, an electric motor which provides relative movement between an authentic document and said sensing element to develop a signal having a given frequency, a frequency-sensing circuit which has a predetermined center frequency that is essentially the same as said given frequency, a current-sensing sub-circuit that senses the value of the current flowing to said motor, and means that will keep said validator from validating a document if the level of said current sensed by said current-sensing sub-circuit exceeds a predetermined value.
 11. A validator as claimed in claim 10 wherein said means includes a selectively-conductive element that can effectively eliminate the output of said frequency-sensing circuit, and wherein said selectively-conductive element of said means will effectively eliminate the output of said frequency-sensing circuit whenever said current-sensing sub-circuit exceeds the level of said current sensed by said predetermined level.
 12. A validator as claimed in claim 10 wherein said current-sensing sub-circuit includes an adjustable member which can be adjusted to set said predetermined value, wherein said adjustable member applies a voltage to one input of a comparator, and wherein a voltage corresponding to the current flowing through said motor is applied to another input of said comparator.
 13. A validator as claimed in claim 10 wherein said means includes a selectively-conductive element, and wherein said selectively-conductive element does not keep said frequency-sensing circuit from sensing and responding to said given frequency but can effectively eliminate the output of said frequency-sensing circuit.
 14. A validator as claimed in claim 10 wherein a speed-regulating feedback loop for said electric motor has amplification therein, and wherein said speed-regulating feedback loop responds to retardation of said document to materially increase the value of the current flowing to said motor, whereby said validator can effectively eliminate the output of said frequency-sensing circuit when even relatively small retardation of said document occurs.
 15. A validator which comprises a document-sensing circuit that can respond to the sensing of an authentic document to develop a predetermined signal, an output circuit, a switch that normally can initiate operation of said document-sensing circuit and thereby normally enable said output circuit to develop an output signal, and a circuit that responds to the development of said predetermined signal to effectively isolate said switch from said document-sensing circuit.
 16. A validator as claimed in claim 15 wherein an electric motor can provide relative movement between said document and a sensing element, wherein said switch can normally initiate operation of said electric motor, and wherein said circuit effectively isolates said switch from said electric motor whenever iT effectively isolates said switch from said document-sensing circuit.
 17. A validator which comprises a sensing device, document-moving members that can move a document inwardly toward and adjacent to said sensing device and then can move said document inwardly beyond said sensing device, means to determine whether said document-moving members have moved said document inwardly beyond said sensing device, and a circuit that can reverse the direction of movement of said document-moving members, said circuit reversing the direction of movement of said document-moving members if said means determines that said document-moving members have not moved said document inwardly beyond said sensing device, said document-moving members providing gripping forces immediately outwardly of said sensing device to enable said document-gripping members to be in register with and to grip the trailing portion of a document which had the major portion of the length thereof wrinkled and crumpled up against said sensing device while said document-moving members were moving said document toward said sensing device.
 18. A validator as claimed in claim 17 wherein said means includes a bill-actuated sensing member that senses the inward movement of the leading edge of said bill.
 19. A validator as claimed in claim 17 wherein a timing sub-circuit will cause said circuit to reverse the direction of movement of said document-moving members if said means does not, within a pre-set length of time, determine that said document-moving members have moved said document inwardly beyond said sensing device.
 20. A validator as claimed in claim 17 wherein said document-moving members are pulley-driven belts, and wherein at least one pulley for each belt is disposed immediately outwardly of said sensing device.
 21. A validator as claimed in claim 17 wherein said sensing device must directly engage said document as it senses said document, and wherein the leading edge of said document must force its way between said sensing device and a pressure-applying element which is in register with said sensing device.
 22. A validator which comprises document-moving members that move a document inwardly of said validator, position-sensing means that senses when a document is moved inwardly to a predetermined position within said paper currency validator, further position-sensing means that senses when said document is moved further inwardly to a second predetermined position within said paper currency validator, a sensing device located intermediate the first said and said further position-sensing means and that can respond to the inward movement of an authentic document relative thereto by said document-moving members to develop a signal, a timing circuit that responds to the sensing by the first said position-sensing means of the inward movement of a document to initiate a time period of predetermined duration, and means to reverse the direction of movement of said document-moving members and thereby move said document outwardly of said validator if said further position-sensing means does not sense the inward movement of said document before the end of said time period. 